The Do-It-All Mountain Bike

Giant's 27.5-inch Mountain Bike Line

In the modern mountain bike era, there have typically been two choices when it comes to wheel size. There are the 29-inchers, which go down the trail like a freight train, easily rolling over roots and rocks but lacking nimbleness in the corners, or the classic 26-inchers, which are far more agile but also require more work as you bang over obstacles. Recently, though, a new common ground has arisen: the 27.5-inch wheel, which claims to achieve most of the rollover advantage of a 29er while maintaining the "flickability" of a 26er.

No brand seems more committed to the 27.5-inch wheel size than Giant, which has roughly 40 models that are equipped with it in this year's lineup. We went to Mountain Creek Bike Park in Vernon, New Jersey, to give them some test runs both up and down the hill. Okay, mostly down.

For our ride, we spent a lot of time on the Enduro race course. For the unfamiliar, Enduro is a unique format that includes several timed runs with both climbing and fast, technical descents. All runs need to be done on the same day, using the same bike, which is why the 27.5-inch bikes are so appealing for the format.

The 2014 Trance SX ($4,050) is a full-on trail bike with 5 inches of travel in both the front and the back. The fork and the rear shock both use air instead of springs, so adjusting the amount of squish they produce is as simple as turning a few knobs to make them stiffer or softer depending on the terrain. It's also equipped with a dropper seat, which makes changing saddle height in the middle of your ride as simple as flipping a switch on the left handlebar.

The SX version comes with Shimano's Zee components, which are built for the durability of downhill and make sense because a technical issue is the kiss of death in an Enduro race. If you want to step up to the Advanced version, the price shoots up to $6,400, but you get a lighter carbon composite frame and step up to the high-end SRAM components.

Once you get on, the most immediate advantage you notice is how much more nimble a 27.5-inch tire-equipped bike is than a 29er, especially in high-speed corners. Less gyroscopic force means it's easier to lean over and take banked turns as they're meant to be taken. It does bang around more through choppy sections, but the extra rolling clearance is tangible over rocks roughly the size of a large fist, or, as mountain bikers call them, baby heads. It's most notable on trudging climbs. Losing traction is bad news in that scenario, so the extra tire contacting the ground is appreciated.

We also got some time on the Giant Anthem Advanced 27.5-inch XC race rigs. At 100mm, one of these has less suspension travel than the Trance, but it also has a more aggressive frame geometry, which makes it more efficient in the climbs and when you're hammering on the pedals. The Anthem Advanced runs anywhere from $3,500 for a race-ready rig up to an $8,250 composite World Cup kit.

Ultimately, a 27.5-incher seems like the real deal. Even many pros seem to be making the switch, especially in the Enduro discipline, and that seems like a good barometer. The idea of one mountain bike that can do everything is that much closer to reality.